Hi there
The way I see them is:-
EP3, lighter, more spartan, lesser build quality (interior) but the more focused B-road car and stripped make OK track cars, though lack of LSD is a bit of a killer.
FN2 is a more solid car, it feels more premium and has a better quality interior and the seats are a massive improvement, a lot more bucket style and more supportive. The FN2 certainly seems to have a better mid-range. But its extra weight and lack of IRS mean they are not quite as capable on a UK road, on a track however the lack of IRS does not really impede the car. I believe LSD was not until 2010 and newer models and this would make them more fun for sure on roundabouts.
Infact to be honest, unless your Michael Schumacher behind the wheel your not gonna be any slower or faster in either on your favourite country road. By this I mean you could have a crap driver in an EP and a half capable driver in the FN2 and the FN2 shall be the quicker car.
If my aim was track weapon, I'd probably go EP and strip it out completely, for the road FN2. But saying that for a track weapon, 5k would build me an epic 328i which having done a lot of trackdays would kick any FWD hatch backside with relative ease, apart from the mega lightweight stuff pushing out some nice horses.
But saying that, try driving a stripped 328i on coilovers on the road, OMG utter headache!